build-flow.api/src/modules/im/Application/Chat/Handlers/SearchMessagesQueryHandler.cs

using System.Text.RegularExpressions;
using BuildFlow.Shared.Domain.Exceptions;
using IM.Application.Chat.DTOs;
using IM.Application.Chat.Queries;
using IM.Domain.Common;
using IM.Infrastructure.Mongo;
using IM.Infrastructure.Persistence;
using MediatR;
using MongoDB.Bson;
using MongoDB.Entities;

namespace IM.Application.Chat.Handlers;

/// <summary>
/// 历史消息搜索处理器。基于 MongoDB 对消息正文、发送者名称和文件名进行模糊检索。
/// </summary>
public class SearchMessagesQueryHandler(
    ImDbContext db,
    IUserInfoService userInfoService) : IRequestHandler<SearchMessagesQuery, MessageHistoryDto>
{
    public async Task<MessageHistoryDto> Handle(SearchMessagesQuery request, CancellationToken ct)
    {
        var isParticipant = await db.ConversationParticipants
            .AnyAsync(p => p.ConversationId == request.ConversationId && p.UserId == request.UserId, ct);

        if (!isParticipant)
        {
            throw new UnauthorizedException("无权搜索该会话的消息");
        }

        var keyword = request.Keyword.Trim();
        if (keyword.Length == 0)
        {
            return new MessageHistoryDto([], false);
        }

        var escaped = Regex.Escape(keyword);
        var regex = new BsonRegularExpression(escaped, "i");

        var messages = await DB.Default.Find<MessageDocument>()
            .Match(f => f.And(
                f.Eq(m => m.ConversationId, request.ConversationId),
                f.Or(
                    f.Regex(m => m.Content, regex),
                    f.Regex(m => m.SenderName, regex),
                    f.Regex("Metadata.FileName", regex))))
            .Sort(m => m.CreatedAt, Order.Descending)
            .Limit(request.Limit)
            .ExecuteAsync(ct);

        var dtos = await ToMessageDtosAsync(messages, ct);
        return new MessageHistoryDto(dtos, false);
    }

    private async Task<List<MessageDto>> ToMessageDtosAsync(List<MessageDocument> messages, CancellationToken ct)
    {
        var senderIds = messages
            .Where(m => string.IsNullOrEmpty(m.SenderAvatar))
            .Select(m => m.SenderId)
            .Distinct()
            .ToList();

        var users = senderIds.Count > 0
            ? await userInfoService.GetUsersAsync(senderIds, ct)
            : new Dictionary<string, (string Username, string? Avatar)>();

        return messages.Select(m =>
        {
            var avatar = m.SenderAvatar;
            if (string.IsNullOrEmpty(avatar))
            {
                avatar = users.GetValueOrDefault(m.SenderId.ToString()).Avatar;
            }

            return new MessageDto(
                m.ID,
                m.ConversationId,
                m.SenderId,
                m.SenderName,
                avatar,
                m.ContentType,
                m.Content,
                m.Metadata != null ? new MessageMetadataDto(
                    m.Metadata.FileName,
                    m.Metadata.FileSize,
                    m.Metadata.FileUrl,
                    m.Metadata.ImageUrl,
                    m.Metadata.ImageWidth,
                    m.Metadata.ImageHeight,
                    m.Metadata.EmojiCode)
                {
                    BucketName = m.Metadata.BucketName,
                    ObjectKey = m.Metadata.ObjectKey,
                    ContentType = m.Metadata.ContentType
                } : null,
                m.ReplyToId,
                m.CreatedAt,
                m.MentionUserIds,
                m.MentionAll,
                m.IsRecalled,
                m.RecalledAt,
                m.RecalledBy,
                m.ForwardFromMessageId,
                m.ForwardFromSenderName,
                m.ForwardFromConversationId);
        }).ToList();
    }
}